This invention relates to a lock device which can be advantageously used to hold in the closed position doors or the like which are hinge-mounted to be freely openable. This invention relates particularly to a lock device which locks when a pressing means such as an engaging member provided on the door is subjected to a first push and unlocks when subjected to a second push to allow the door to open.
Conventional lock devices are already known and have been put to practical use in which two pushes in the same direction are used, the first push locking the lock and the second push unlocking the lock.
A number of such lock devices have been proposed which are structurally different. Representative of such known lock devices include those which employ a rotating cam plate and those having a heart-shaped groove in which is slidably engaged a springy pin which can only move in one direction.
The former type of lock device is provided with a case and a sliding member which can slide into or out of the case, and which bears the oblong rotating cam plate which is provided with two engaging portions, the length of the rotating cam plate being always aligned with the sliding member, and when a first push causes the sliding member to enter the case, a notch-shaped engaging portion located on the tip of the cam plate contacts a projection provided on the case, causing the cam to turn slightly and an identical notch-shaped engaging portion formed on the rear end to move transversely out of alignment with the sliding member, and when the sliding member is urged back by the force of a spring the engaging portion on the rear end engages with the engaging portion provided on the case, preventing the retraction of the sliding member to put the lock device into a locked state. With a second push, the sliding member enters further into the case, and utilizing this, the engaging portion at the front end again comes into contact with the projection, turning the cam plate slightly and disengaging the rear end engaging portion, enabling the lock to be unlocked. Locking and unlocking is thus done by the two pushes, the construction being such that in between the rotating cam plate is turned through a half revolution.
The latter device consists of a cam plate with a heart-shaped groove and a springy pin which slidably engages in the groove. The floor of the groove is sloped and stepped at several places so as to permit movement in one direction only, and the tip of the pin is moved along while being pressed against the floor of the groove. With the first push the pin moves along the groove and is guided into the valley of the heart shape where it engages to put the lock device into a locked state, while the next push dislodges it from the valley and returns it to its original state, unlocking the lock.
Both types of devices have been put into practical use, but with the former, as just a slight turn of the rotating cam plate enables the engagement of the engaging portion and the locking and unlocking of the lock, a high degree of precision is required with respect to the relative positions of the parts, and, especially when the device was made smaller, the small manufacturing tolerance involved gave rise to malfunctioning. Also with regard to this rotating cam plate type lock device, because its operation did not provide a feeling that it was snapping into place, said operation did not give the user any tactile information, and it therefore was necessary to check visually.
In the case of the latter type of lock device, when the pin being moved along the groove mounted the slopes provided on the floor of the groove and dropped at the steps, the tip of the pin struck the floor with a sharp click as it engaged with the valley of the heart, locking the lock, and when the pin was subsequently dislodged from the base, unlocking the lock, the positive click it gave provided a fully adequate tactile sensation of the operation. However, on the other hand, with the lock device of this conventional heart-shaped groove type, the complexity of the pin action meant also that it was structural complex, and this was a major hindrance, especially with respect to making the device smaller.
Specifically, in the operation of sliding the pin along the heart-shaped groove, the tip of the pin oscillates transversely to follow the heart shape, and this movement has to be accompanied by the sliding contact of the pin tip with the groove floor under a constant spring pressure, and by vertical motion in accordance with the slopes and steps provided in the floor of the groove, so it is necessary for the pin to be of a material with good resistance to deformation, such as steel wire, and it was also necessary to provide the device with another means to exert the spring-pressure on the floor of the groove, which was troublesome in terms of the relationship of the parts in the assembly and also meant more parts, which naturally hindered any downsizing of the device.